WO2007142194A1

WO2007142194A1 - Communication system, transmission device, reception device, and synchronization method

Info

Publication number: WO2007142194A1
Application number: PCT/JP2007/061297
Authority: WO
Inventors: Mariko Matsumoto
Original assignee: Nec Corporation
Priority date: 2006-06-09
Filing date: 2007-06-04
Publication date: 2007-12-13
Also published as: JPWO2007142194A1; CN101467373A; US8489133B2; US20100178877A1; KR20090018959A

Abstract

A receiver (2) successively and stepwise switches a preset frequency change amount from a large value to a small value. According to a reception side frequency change amount, a reception side frequency candidate for detecting a synchronous signal is calculated. A synchronous signal detection unit (5) detects a synchronous signal transmitted from a transmission device by using the calculated reception side frequency candidate. Moreover, a transmitter (1) calculates a transmission side frequency candidate as a frequency candidate for transmitting the synchronous signal according to the greatest frequency change amount calculated according to the band width of the synchronous signal. When the calculated transmission side frequency candidate exists in the system frequency band, the calculated transmission side frequency candidate is decided to be a synchronous signal frequency for transmission of the synchronous signal and the synchronous signal is transmitted from a synchronous signal transmission unit (4) to the receiver (2).

Description

Specification

COMMUNICATION SYSTEM, TRANSMISSION DEVICE, RECEPTION DEVICE, AND SYNCHRONIZATION DETECTION METHOD

Technical field

The present invention relates to a communication system, a transmission device, a reception device, and a synchronization detection method for detecting an effective frequency for transmitting and receiving information from a plurality of candidate frequencies.

Background art

Conventionally, in a communication system using a mobile station such as a mobile terminal, a plurality of frequencies are defined as frequencies of a downlink signal transmitted from a base station to a mobile station. Then, one or more of these multiple frequencies are selected, and the downlink signal is transmitted using the selected frequencies.

FIG. 1 is a diagram schematically showing a frequency domain in order to explain a band search that is a conventional frequency domain search.

[0004] For example, in 3GPP (3rd Generation Partnership Project), which is a W-CDMA (Wideband Code Division Multiple Access) standard, as shown in Fig. 1, 2.5 MHz at both ends between 2110 MHz and 2170 MHz. In the frequency range excluding, 276 frequencies called rasters are set at intervals of 200 kHz. Then, an effective frequency is selected from the set frequencies, and a downlink signal is transmitted using a transmission band centered on the selected effective frequency. Raster is defined as the smallest unit that places the center frequency in the transmission band of the system.

[0005] In addition, the mobile station detects an effective frequency from candidate frequencies when power is turned on or when out-of-service is detected, and further establishes synchronization with the base station. This process of detecting the effective frequency is called a band search process. A known signal called a synchronization signal may be used to detect the effective frequency. As a method of speeding up the band search process, a method of blocking a plurality of adjacent frequencies has been proposed (see, for example, Japanese Patent Publication No. 2003-244083).

[0006] In 3GPP Release7, multiple transmission bandwidths (1.25, 2.5, 5, 5, 10, 15, 20MHz) can be set from narrow to wide within the frequency band owned by the operator. When (See, for example, 3GPP TR 25.814.V1.1.1 (2006-2) Physical Layer Aspects for Evolved UTRA (Release 7) 7.1.1).

[0007] Further, regarding such a system in which a plurality of bandwidths can be set, the center frequencies of the plurality of bandwidths are matched, and the center frequency is an integral multiple of the raster, and the synchronization signal CH (Synchronization channel) is the center. (For example, see 3GPP Rl-060311 SCH Structure and Cell Search Method for E—UTRA Downlink).

[0008] On the other hand, in recent years, including 3GPP Release7, 3GPP Long Term Evolution (LTE) ゝ WiMAX, OFDM (Orthogonal Frequency Division Multiplexing) / OFDM A (Orthogonal Frequency Division Multiplexing Access) Tend to be used in mobile communications. At that time, parameters such as the subcarrier interval are set in consideration of fading resistance, so the subcarrier interval may not be an integer multiple of the raster, and it is difficult to simplify the band search processing and synchronization processing. It becomes.

However, according to the above-described method, the presence / absence of an effective wave is sequentially searched using a large number of set candidate frequencies, so that band search processing for detecting an effective frequency is performed. There is a problem that it takes a long time.

[0010] In addition, a large amount of computation is required to sequentially search for the presence or absence of effective waves for a large number of frequencies. Further, when OFDM is used as the transmission method, if the subcarrier interval is not an integer multiple of the raster, a candidate and In the calculation for each frequency, the intermediate results cannot be referred to each other, so that the amount of calculation cannot be reduced, thereby increasing the power consumption required for the band search process.

Disclosure of the invention

In order to solve the above-described problem, an object of the present invention is to provide a communication system, a transmission device, a reception device, and a synchronization detection method capable of realizing effective frequency detection processing at high speed.

[0012] To achieve the above object, the present invention provides:

In a communication system comprising: a transmission device that transmits a synchronization signal for establishing synchronization; and a reception device that establishes synchronization by detecting the synchronization signal; The receiving device sequentially switches from the thinned thinned interval to the non-thinned one for performing the detection of the synchronization signal,

The transmitter is set to transmit the synchronization signal at an interval that is roughly thinned out by the receiver.

[0013] Further, the synchronization is frequency synchronization, and the synchronization establishment is detection of an effective communication frequency,

The receiving apparatus sequentially switches a preset frequency change amount from a large value to a small value, calculates a reception-side candidate frequency for detecting the synchronization signal based on the frequency change amount, The synchronization signal is detected using the calculated reception candidate frequency,

The transmitter is calculated based on a system bandwidth for performing communication of the communication system.

When a transmission-side candidate frequency that is a frequency candidate for transmitting the synchronization signal is calculated based on the frequency change amount that is as large as possible, and the transmission-side candidate frequency exists in the system frequency band, the transmission frequency The side candidate frequency is determined as a synchronization signal frequency for transmitting the synchronization signal.

[0014] Further, the receiving apparatus adds an offset to an integral multiple of the reception-side frequency change amount to obtain the reception-side candidate frequency,

The transmission apparatus is characterized in that an offset is added to an integral multiple of the transmission-side frequency change amount to obtain the transmission-side candidate frequency.

[0015] Further, the receiving apparatus sets the offset to 0,

The transmitting apparatus sets the offset to 0.

[0016] Further, the transmission device transmits a known signal as the synchronization signal,

The receiving apparatus detects a match between the reception-side candidate frequency and the known signal, or a match between the known signal and a replica signal calculated using IFFT or FFT.

The calculated replica signal is stored.

[0017] Further, the transmission device transmits a signal repeating the same pattern as the synchronization signal. The receiving apparatus detects the synchronization signal by delay detection.

[0018] Further, the transmission apparatus is characterized in that the transmission side frequency change amount is set to an integral multiple of a minimum arrangement unit of a center frequency of the system band.

[0019] Further, the receiving apparatus is characterized in that the receiving side frequency change amount is set to an integral multiple of a minimum arrangement unit of a center frequency of the system band.

[0020] Further, a transmission device that transmits a synchronization signal for synchronization within a system frequency band to a reception device,

Based on the largest possible transmission-side frequency change amount calculated based on the bandwidth of the synchronization signal, a transmission-side candidate frequency that is a frequency candidate for transmitting the synchronization signal is calculated, and the transmission-side candidate frequency is calculated. Is present in the system frequency band, the transmission side candidate frequency is determined as a synchronization signal frequency for transmitting the synchronization signal.

[0021] Furthermore, an offset is added to an integral multiple of the transmission-side frequency change amount to obtain the transmission-side candidate frequency.

[0022] Further, the offset is set to 0.

[0023] Also, a receiving device that receives the synchronization signal transmitted from the transmitting device,

The reception side frequency change amount set in advance is sequentially switched from a large value to a small value, and the reception side candidate frequency for detecting the synchronization signal is calculated based on the reception side frequency change amount. The synchronization signal is detected using the calculated candidate frequency on the receiving side.

[0024] In addition, an offset is added to an integral multiple of the reception-side frequency change amount to obtain the reception-side candidate frequency.

[0025] Further, the offset is set to 0.

[0026] Further, synchronization in a communication system including a transmission device that transmits a synchronization signal for synchronization within the system frequency band and a reception device that detects the synchronization signal within the system frequency band. A detection method,

A process of sequentially switching the reception device from performing the synchronization signal detection trial to a non-thinned one roughly And a process of setting the transmission so that the synchronization signal is detected at an interval obtained by roughly thinning out the synchronization signal of the reception device.

[0027] In addition, the receiving device, a process of switching a preset frequency change amount from a large value to a small value sequentially step by step,

A process in which the receiving apparatus calculates a receiving-side candidate frequency for detecting the synchronization signal based on the receiving-side frequency change amount;

A process in which the receiving device detects the synchronization signal using the calculated reception candidate frequency;

A process of calculating a transmission-side candidate frequency that is a frequency candidate for transmitting the synchronization signal based on the frequency change amount that is as large as possible calculated based on the bandwidth of the synchronization signal;

A process in which the transmission device determines the transmission-side candidate frequency as a synchronization signal frequency for transmitting the synchronization signal when the transmission-side candidate frequency is present in the system frequency band;

The transmission device includes a process of transmitting the synchronization signal to the reception device using the synchronization signal frequency.

[0028] The reception-side frequency change amount and the transmission-side frequency change amount include the same value.

[0029] In the present invention configured as described above, a synchronization signal for synchronization within the system frequency band is transmitted by the transmission device, and the frequency at which the reception device attempts to detect the synchronization signal is determined. Roughly thinning out and switching from thin to thin bow I kana sequentially, the synchronization signal is detected within the system frequency band.

Accordingly, it is possible to realize a high-speed processing for detecting an effective frequency from among a plurality of frequency candidates and a reduction in power consumption required for the processing.

[0031] As described above, in the present invention, a synchronizing signal for synchronizing within the system frequency band is transmitted by the transmitting device, and the frequency at which the receiving device attempts to detect the synchronizing signal is coarsened. Switching from thinned out to non-thinned one by one, and configured to detect the synchronization signal within the system frequency band, and the transmitting device has set the synchronizing signal transmission frequency so that it can be detected early by the receiving device. To achieve high speed Togashi.

Brief Description of Drawings

FIG. 2 is a diagram showing an embodiment of a communication system of the present invention.

[FIG. 3 (a)] FIG. 3A is a diagram schematically showing a first-stage frequency region in order to explain a step-by-step search for synchronization channels in the configuration shown in FIG.

[FIG. 3 (b)] FIG. 3B is a diagram schematically showing a second-stage frequency region in order to explain a step-by-step search of the synchronization channel in the form shown in FIG.

[FIG. 3 (c)] FIG. 3C is a diagram schematically showing a third-stage frequency region in order to explain the step-by-step search of the synchronization channel in the configuration shown in FIG.

FIG. 4 is a diagram showing the effect of the band search fast key of the present invention.

FIG. 5 is a flowchart for explaining a synchronization detection method in the receiver of the communication system shown in FIG. 2.

FIG. 6 is a flowchart illustrating the flowchart shown in FIG. 5 in more detail.

[FIG. 7 (a)] FIG. 7A is a diagram schematically illustrating the first step of the stepwise band search process described with reference to the flowchart shown in FIG.

[FIG. 7 (b)] FIG. 7B is a diagram schematically showing the second stage processing of the stepwise band search processing described using the flowchart shown in FIG.

[FIG. 7 (c)] FIG. 7C is a diagram schematically illustrating the third step of the stepwise band search process described using the flowchart shown in FIG.

[FIG. 7 (d)] FIG. 7 (d) is a diagram schematically illustrating the fifth stage process of the stepwise band search process described with reference to the flowchart shown in FIG.

8 is a flowchart for explaining a procedure for determining a transmission frequency of a synchronization signal in the transmitter of the communication system shown in FIG.

FIG. 9 is a flowchart for explaining another determination method according to the procedure for determining the transmission frequency of the synchronization signal in the transmitter of the communication system shown in FIG. 2.

[Fig. 10 (a)] The transmission band in the frequency domain of the synchronization signal in the present invention is TBW-si This is a diagram schematically showing V in a system for transmitting an OFDM signal composed of 301 subcarriers with 5 MHz.

[Fig. 10 (b)] The arrangement of the synchronization signal in the frequency domain according to the present invention is schematically shown in a system in which the transmission band is TBW—S2 = 1.25 MHz and an OFDM signal composed of 705 subcarriers is transmitted. FIG.

FIG. 11 is a diagram schematically showing a time domain and a frequency domain of a general subcarrier in 3GPP LTE.

FIG. 12 is a diagram schematically showing a time domain and a frequency domain of subcarriers in the present invention.

FIG. 13 is a diagram schematically showing the time domain and frequency domain of subcarriers in a system that does not require DC subcarriers.

FIG. 14 is a diagram schematically showing subcarriers on the frequency axis when a synchronization signal is transmitted in a system provided with DC subcarriers.

FIG. 15 is a diagram schematically showing subcarriers on the frequency axis when transmitting a synchronization signal in a system in which it is not necessary to provide DC subcarriers.

FIG. 16 is a diagram showing an embodiment when the communication system of the present invention is applied to a wireless communication system using a wireless communication system.

[FIG. 17 (a)] FIG. 17A is a diagram showing a first form when another configuration is used for the part shown by a broken line in the form shown in FIG.

[FIG. 17 (b)] FIG. 17B is a diagram showing a second form in the case where another configuration is used in the part shown by a broken line in the form shown in FIG.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a diagram showing an embodiment of a communication system according to the present invention.

As shown in FIG. 2, the present embodiment includes a transmitter 1 that is a transmission device and a receiver 2 that is a reception device that communicates with the transmitter 1. Further, the transmitter 1 includes a synchronization signal generation unit 3 and a synchronization signal transmission unit 4. The receiver 2 includes a synchronization signal detection unit 5 and a frequency control unit 6. Synchronization signal generator 3 is connected between transmitter 1 and receiver 2. A synchronization signal for synchronization is generated in between. The synchronization signal transmission unit 4 transmits the synchronization signal generated by the synchronization signal generation unit 3 to the receiver 2. The frequency control unit 6 outputs a frequency for detecting the synchronization signal transmitted from the transmitter 1 to the synchronization signal detection unit 5. The synchronization signal detection unit 5 detects the synchronization signal using the frequency output from the frequency control unit 6 and notifies the frequency control unit 6 of the detection result.

FIG. 3 is a diagram schematically showing a frequency domain in order to explain the stepwise search of the synchronization channel in the form shown in FIG.

[0037] As shown in FIG. 3, the frequency control unit 6 of the receiver 2 changes the candidate frequency for detecting the synchronization signal from a coarsely thinned out predetermined frequency band to a non-thinned one. Output while switching step by step.

[0038] In Fig. 3, (a) shows the candidate frequencies to be tried in the first stage of synchronization detection.

(B) shows the second stage candidate frequency, and (c) shows the third stage candidate frequency. As the stage progresses, the interval between candidate frequencies becomes smaller.

In the transmitter 1, the transmission frequency of the synchronization signal transmission unit 4 is set so that the synchronization signal is placed on an earlier frequency output by the frequency control unit 6 of the receiver 2.

FIG. 4 is a diagram showing the effect of speeding up the band search of the present invention.

[0041] As shown in FIG. 4, the process according to the present invention described above is higher in the stage of the band search and the detection probability can be obtained in comparison with the conventional method.

[0042] The synchronization signal generated by the synchronization signal generation unit 3 of the transmitter 1 may be one that repeats the same pattern on the time axis or a signal that is known between transmission and reception. Also receiver

The synchronization signal detection unit 2 of 2 detects the synchronization signal by delay detection when the same pattern is repeated on the time axis, and attempts detection by synchronization detection if the synchronization signal is a known pattern. Further, the configuration of the synchronization signal and its detection unit may be any method that does not limit the effect of the present invention.

[0043] Further, as described in Japanese Patent Publication No. 2003-244083, power is detected by dividing the search frequency band into a plurality of blocks, and the band of the power is detected by the method of the present invention. You can do the search process!

[0044] Hereinafter, a synchronization detection method in the communication system shown in FIG. 2 will be described. FIG. 5 is a flowchart for explaining a synchronization detection method in receiver 2 of the communication system shown in FIG.

[0046] Here, BSS—UE (k) is defined as the reception side frequency change amount (band search step) in the k-th search step, as shown in Table 1.

[0047] [Table 1]

[0048] First, in step 1, the variable k is set to 0, which is an initial value, and synchronization detection of an effective frequency that is a candidate frequency on the receiving side is performed in step 2 by band search of BSS—UE (0) width. Is called. Whether the effective frequency is detected or not is determined in step 3, and if it is detected, the process ends.

[0049] On the other hand, if an effective frequency is not detected, it is determined in step 4 whether or not there is a next candidate frequency on the receiving side by a band search of BSS-UE (0) width. In other words, with a simple example, the search frequency band power for effective frequency synchronization detection is 2000 MHz to 2005 MHz, and the candidate frequency force for which synchronization detection was first performed is 2003. 2 MHz. Since the BSS—UE (O) width is 3.2 MHz, the next candidate frequency is 2006. 4 MHz, which exceeds the frequency band, and the next candidate frequency does not exist. The example given here uses a set value for convenience of explanation, and is not a value actually used.

[0050] When it is determined in step 4 that the next candidate frequency exists by the band search of BSS—UE (0) width, the next candidate frequency force S is set in step 5 and synchronized in step 2. Detection is performed.

[0051] Also, in step 4, when it is determined that there is no next candidate frequency by the band search of BSS—UE (0) width, that is, the effective frequency by the band search of BSS—UE (O) width. If it is determined that the wave number detection process has been completed, the BSS—UE (0) value is compared with the raster value in step 6. Here, the raster value is 200 kHz. Also, BSS U The value of E (k) is an integer multiple of the raster value.

[0052] BSS— Since the value of UE (0) is larger than the raster value, in step 7, k = k

The process is the same as the process in BSS-UE (O) from step 2 for the next stage BSS-UE (1).

[0053] Unless an effective frequency is detected in any power of BSS-UE (k), steps 2 to 7 are performed until the value of BSS-UE (k) becomes equal to or less than the raster value. As explained in Fig. 3, the frequency change on the receiving side is switched from a large value to a small value, that is, the candidate frequency is gradually switched from a coarsely thinned out frequency within a predetermined frequency band to a non-thinned one. However, synchronization detection is performed. If the effective frequency is not detected even if the value of BSS—UE (k) falls below the raster value, it is determined that there is no effective frequency in the search band.

FIG. 6 is a flowchart that further embodies the flowchart shown in FIG.

[0055] Here, the bandwidth of the synchronization signal is SCH-BW. The lower limit frequency of the search frequency band for detecting the effective frequency is f-L, and the upper limit frequency is f-H.

[0056] First, as shown in Equation 1, in step 11, the variable k is set to 0, which is an initial value, and synchronization detection is started from the maximum band search step BSS-UE (0).

[0057] [Equation 1] k: Q ■■■ (Formula 1)

[0058] In step 12, Ntmp is calculated using Equation 2. Here, [] shall be rounded down to the next decimal place.

[0059] [Equation 2] L ⁺ SCH_BW / 2) JBSSJJE (k)] (Formula 2)

[0060] In step 13, (f_L + SCH- BW / 2) and (Ntmp X BSS

_UE (k)) is compared.

[0061] [Equation 3] f_ _L + SOI_Bf / 2 --N _tap BSS_UE (k)… (Formula 3)

If it is determined in step 13 that (f_L + SCH−BWZ2) and (NtmpXBSS_UE (k)) are not equal, calculation of equation 4 is performed in step 14.

[0063] [Equation 4] +1 ... (Equation 4) Here, as a result of calculation of Equation 2, Equation 3, and Equation 4, if there is a value less than the decimal point in [] of Equation 2, rounding up operation I do.

[0064] Then, (f 1 H—SCH—BWZ2) and (Ntmp X BSS_UE (k)) are compared by Equation 5, and the candidate frequency force f—H for performing the band search is compared with SCH—BWZ2 In step 15, it is determined whether the value is less than the margin.

[0065] [Equation 5]

_H SCH_BW / 2: N _tmp X BSS ^ UE (k)… (Formula 5)

[0066] If it is determined in step 13 that (f_L + SCH-BWZ2) and (Ntmp X BSS_UE (k)) are equal, step 14 is not performed and step 15 is performed. Is called.

[0067] If it is determined in step 15 that the (NtmpXBSS—UE (k)) force S (f—H—SCH—BWZ2) or less, the candidate frequency f (k , Ntmp) is calculated.

[0068] [ _Equation 6] f {k, N _tBp ) = BSS_UE {k) XN _tap (Equation 6)

[0069] Then, synchronization detection is performed in step 17 for the candidate frequency f (k, Ntmp) calculated according to Equation 6, and whether or not synchronization is detected is determined and detected in step 18. If it is found, the band search process ends.

On the other hand, if no synchronization is detected in step 18, Ntmp is incremented by 1 according to equation 7 in step 19, and the process of step 15 is performed again. [0071] [Equation 7]

N _tmp = N _tap + l… (Formula 7)

[0072] If it is determined in step 15 that (Ntmp X BSS_UE (k)) is greater than (f_H—SCH—BWZ2), step 6 and step 7 described in FIG. In the same way as the above process, the band search process is executed by increasing k by 1 in step 21 until it is determined in step 20 that k has exceeded the maximum value (4 in this example).

[0073] If synchronization is not detected even if k exceeds the maximum value, it is determined that there is no effective frequency within the search band.

FIG. 7 is a diagram schematically showing the stepwise band search process described using the flowchart shown in FIG.

[0075] Figure 7 (a) shows the candidate frequencies for which synchronization detection is performed in the first stage of the stepwise band search. In the first stage, the candidate frequencies f (0, 0) and f (0, 0, Synchronization detection with 1) is performed. At this time, the difference between f (0, 1) and f (0, 0) is BSS—UE (O).

FIG. 7 (b) shows candidate frequencies for which synchronization detection is performed in the second stage. In the second stage, four candidate frequencies f (1, 0) to f (1, 3) exist within the search frequency band for BSS—UE (1). Since f (l, 1) and f (l, 3) have already attempted synchronization detection in the first stage and are not detected, the synchronization detection process is not performed again.

Similarly, FIG. 7 (c) shows candidate frequencies for which synchronization detection is performed in the third stage. In the third stage, there are eight candidate frequencies f (2, 0) to f (2, 7) in the search frequency band for BSS—UE (2), and f (2, 0), f (2, 2), f (2, 4), f (2, 6) have already attempted synchronization detection in the first and second stages, and because of the strong frequencies that have not been detected, The synchronization detection process is not performed again.

Similarly, FIG. 7 (d) shows candidate frequencies for which synchronization detection is performed in the fifth stage. At this time, since BSS-UE (4) is equal to Raster, all band searches can be executed with raster accuracy as in the past.

FIG. 8 shows the transmission frequency of the synchronization signal in transmitter 1 of the communication system shown in FIG. It is a flowchart for demonstrating the procedure to set.

[0080] When the band search is performed in the receiver 2, the frequency at which the synchronization signal detection is attempted is determined by changing the step size step by step. On the other hand, among the multiple band search steps, transmitter 1 sets the frequency fp—si for transmitting the synchronization signal within the transmission band of the system (fL—sl to fH—si) (SCH—BW). To ensure the maximum band search step.

First, the maximum band search step cut 31 is set so that the frequency is most thinned out. A synchronization signal frequency for inserting a synchronization signal is calculated as a transmission-side candidate frequency by a predetermined formula using the set band search step. In step 32, it is determined whether the synchronization signal can be transmitted at the calculated transmission-side candidate frequency, that is, whether the transmission-side candidate frequency is present in the system frequency band.

[0082] If it is determined that transmission is not possible, the band search step is set to a small value sequentially in step 33, that is, it is changed to one that is not thinned out. The transmission side candidate frequency is calculated again using the changed band search step. It is determined whether the synchronization signal can be transmitted at the calculated transmission-side candidate frequency. If it is determined that transmission is possible, the transmission-side candidate frequency is determined as the synchronization signal frequency in step 34.

FIG. 9 is a flowchart for explaining another determination method in accordance with the procedure for determining the transmission frequency of the synchronization signal in transmitter 1 of the communication system shown in FIG.

Here, BSS-tmp is defined as a variable for obtaining the maximum band search step BSS-si which is the maximum transmission side frequency change amount.

First, the minimum value of the band search step is set. That is, the raster value Raster is set as shown in Equation 8 in step 41 as the initial value of the band search step.

[0086] [Equation 8]

BSS—ttnp Raster… (Formula 8)

At this time, if the raster is defined, the minimum value of the preset band search step is set.

[0088] Then, in Step 42, NL-tmp is calculated using Equation 9. Where mouth is the value in the mouth Shall be rounded down.

[0089] [Equation 9]

N _L _ _tap = [(f _L _s ^ SCH_BW / 2) / BSS_ tmp]… (Equation 9)

[0090] Then, in step 43, (fL-si) and (NL-tmpXBSS-tmp) are compared by Equation 10.

[0091] [number _{_{_{10] f L _ 3l -N L}}} tap .BSS_twp ... ( Equation 1 0)

[0092] If it is determined in step 43 that (fL-si) and (NL_tmpXBSS_tmp) are not equal, calculation of equation 11 is performed in step 44.

[0093] [Equation 11]

N _L _ _tw -N _L _ _tm ^ \… (Formula 1 1)

[0094] Here, as a result of the calculations of Expressions 9, 10, and 11, if there is a value below the decimal point in the division in [9] of Expression 9, an operation of rounding up the value is performed.

[0095] Then, in step 45, the variable NH-tmp is calculated according to Equation 12. If it is determined in step 43 that fL-si and (NL-tmpXBSS-tmp) are equal, step 44 is not performed and step 45 is performed.

[0096] [Equation 12]

N _{H tap} = [{f _{H sl} + SCH_BW / 2) / BSS—tmp]… (Formula 1 2)

[0097] After that, in Step 46, NL-tmp and NH-tmp are compared by Equation 13.

[0098] [Equation 13]

N _L _ _tmp -N _H _ _tmp … (Formula 1 3)

[0099] If it is determined that NL—tmp and NH—tmp are not equal, BSS—tmp has not reached the maximum value. The value of —tmp is calculated to a large value. Then, the processing of steps 42 to 45 is performed again.

[0100] [Equation 14]

BSS_tmp = BSS_tmp ^ 2… (Formula 14)

[0101] On the other hand, if it is determined that NL—tmp is equal to NH—tmp, BSS—tmp has reached the maximum value, and a synchronization signal is transmitted according to Equations 15, 16, and 17. The frequency fp—s 1 is determined in step 48.

[0102] [Equation 15]

H _tap … (Equation 1 5) [0103] [Equation 16]

BSS_s \: BSS one tmp ... (Formula 16)

[ _Equation 17] f _nsl = N _si X BSS_s l… (Equation 1 7)

Thus, the determination of the frequency at which the synchronization signal is transmitted on the transmission side is made by changing the band search step from a small value to a small value, or from a small value to a large value. It can be obtained regardless.

FIG. 10 is a diagram schematically showing the arrangement of the synchronization signals in the frequency domain according to the present invention. Here, an OFDM signal is assumed.

In FIG. 10 (a), it is assumed that the transmission band of the system is TBW—sl = 5 MHz, and an OFDM signal composed of 301 subcarriers is transmitted. Fc-si is the center frequency of system si. The band SCH-BW of the synchronization signal SCH is set to 1.25 MHz, and the center frequency fp-si of the synchronization signal can be set independently of the system center frequency fc-si.

[0108] At this time, TBW si is larger than SCH BW, so the raster is sufficiently small. In this case, a large BSS-si can be selected in the processing described with reference to the flowchart of FIG. 8 or FIG.

[0109] Hereinafter, specific numerical examples will be described.

[0110] As a specific example, fL_sl = 2130. 9MHz, fc_sl = 2133. 4MHz, fH_sl = 213 5. 9MHz, Raster = 200kHz, the maximum value of the band search step is 6.4MHz, and the subcarrier spacing Δ ί = 15kHz And Here, according to the flowchart shown in FIG. 8, the maximum value force of the band search step will be described with the band search step sequentially reduced.

[0111] First, in the maximum band search step 6.4 MHz, a band with a margin of SCH-BW in the transmission band 2131. 525 MHz to 2135. 275 MHz f¾ [this, node search step 6. An integer multiple of 4 MHz and It is determined whether or not a synchronization signal frequency exists. Here, there is no sync signal frequency that is an integer multiple of 4 MHz in the band search step.

[0112] Therefore, the band search step is set to 3.2 MHz in the next stage, and it is determined whether or not there is a synchronization signal frequency that is an integer multiple of the band search step 3.2 MHz between the band 2131.525 MHz and 2135.275 MHz. The In this case, 213.4 MHz exists as a candidate.

[0113] However, 2134. 4MHz has a difference of 1MHz from fc-si and is not divisible by 15kHz which is Δί. This means that this frequency is not a subcarrier frequency, so the subcarrier where the synchronization signal is placed does not match the subcarrier frequency of the system, so it is determined that setting to fp-si is inappropriate. In addition, the band search step is set to 1.6 MHz in the next stage. Between 2131. 525 MHz and 2135. 275 MHz, there are two candidates for the sync signal frequency that is an integer multiple of 1.6 MHz for the node search step: 2112.8 MHz and 2134.4 MHz.

[0114] Here, the difference from fc-si at 2123.8 MHz is 600 kHz, and since it is divisible by Δί, it is determined that the subcarrier on which the synchronization signal is placed matches the subcarrier frequency of the system. si = 2132. 8 MHz. At this time, fp-si is subcarrier number 111.

[0115] Next, in Fig. 10 (b), the transmission bandwidth of the system TBW s2 = l. It is assumed that an OFDM signal having subcarrier power is transmitted. Fc-s2 is the center frequency of system s2. The band SCH-BW of the synchronization signal SCH is 1.25 MHz.

[0116] For example, in the processing described using the flowchart shown in FIG. 9, TBW-s2

= Because SCH—BW, BSS—s2 = Raster, and fp—s2 = fc—s2.

[0117] In the above description, in Equation 6 and Equation 17, the power obtained by setting the frequency of the synchronization signal to an integer multiple of the band search step may be added to the integer multiple of the band search step to obtain Equation 18 and Equation 19. .

[0118] [Equation 18] fp_ _s

… (Equation 1 8) [0119] [Equation 19] f offset (n N _tap ) 2 f _offset BSS_UK, k, XN _tap … (Equation 1 9)

[0120] In accordance with Equation 18 and Equation 19, Equation 2 in the processing described with reference to the flowchart shown in FIG. 6, Equation 3 in Equation 21, Equation 21 in Equation 5, Equation 5 in Equation 22, 6 can be replaced by Equation 19.

[0121] [Equation 20]

Ν _τα = [(f_ _L -f _offset + SCH_BW / 2) / BSS_UK (k) l… (Equation 2 0) [0122] [Equation 21]

N _tap BSS_UK {k)… (Equation 2 1) [0123] [Equation 22] f _H ~ f offset- SCH_BW! 2: N _tap X BSS— UK (k)… (Equation 2 2)

[0124] FIG. 11 is a diagram schematically illustrating a time domain and a frequency domain of a general subcarrier in 3GPP LTE.

[0125] As shown in Figure 11, in 3GPP LTE, the DC (Direct Current) component of the receiver For the simple configuration of the cut, the subcarriers at the center frequency of the system band are defined as DC subcarriers and subcarriers different from normal subcarriers. No data is transmitted on the defined subcarrier. System s3 is configured with normal data transmission subcarriers 133, 135, 139, 141 and DC subcarriers 134, 140 that do not transmit data of the system band TBW—s3 center frequency fc—s3 . Further, subcarriers 130, 132, 136, and 138 of the synchronization signal in the band SCH-BW are inserted at a predetermined synchronization signal insertion period, and the center frequency regions 131 and 137 are regions in which the synchronization signal is not transmitted.

FIG. 12 is a diagram schematically showing the time domain and frequency domain of subcarriers in the present invention.

[0127] As shown in FIG. 12, the system s4 includes normal data transmission subcarriers 145, 147, 151, and 153, and a DC subcarrier that does not transmit data of the center frequency fc—s4 of the system band TBW—s4. , 152 and force. In addition, subcarriers 142, 144, 148, 150 of the synchronization signal shifted from the center frequency fc—s4 are inserted at a predetermined synchronization signal insertion period, and the subcarriers having the center frequency region 143,149 of the center frequency fp—s4 are inserted. The carrier does not transmit a synchronization signal like DC subcarriers 146 and 152.

[0128] Also, in a system in which it is not necessary to provide a DC subcarrier in the relationship between the subcarrier interval and the receiver, the configuration for not including data in the center frequency fc of the system is that the center frequency fc is subcarrier. It can be realized by setting the frequency between.

[0129] Fig. 13 is a diagram schematically showing the time domain and frequency domain of subcarriers in a system that does not require the provision of DC subcarriers.

[0130] As shown in FIG. 13, the system s5 is composed of normal data transmission subcarriers 157, 159, 163, and 165, and the center frequency fc—s5 of the system band TBW—s5 is the data communication subcarrier. Frequency regions 158 and 164 between 157 and 163 and the data communication subcarriers 159 and 165 are obtained. Also, synchronization signal subcarriers 154, 156, 160, and 162 shifted from the center frequency fc—s5 are inserted at a predetermined synchronization signal insertion period, and the center frequency fp—s5 is the synchronization signal subcarrier 154. , 160 and the subcarriers 156, 162 of the synchronization signal become frequency regions 155, 161.

[0131] Figure 14 shows the frequency at the time of synchronization signal transmission in a system with DC subcarriers. FIG. 6 is a diagram schematically showing a subcarrier on an axis.

[0132] As shown in FIG. 14, the synchronization signal is also composed of subcarriers 170 and 172 including the synchronization signal, and DC subcarrier 171. DC subcarrier 171 is arranged at the center frequency fp of the synchronization signal and does not include the synchronization signal.

[0133] Also, in a system that does not require the provision of DC subcarriers, the configuration for not including the synchronization signal in the center frequency fp of the synchronization signal is to set fp to the frequency between the subcarriers including the synchronization signal. Can be realized.

FIG. 15 is a diagram schematically showing subcarriers on the frequency axis at the time of synchronization signal transmission in a system in which it is not necessary to provide DC subcarriers.

As shown in FIG. 15, the synchronization signal is composed of subcarriers 173 and 174 including the synchronization signal. Then, the center frequency fp of the synchronization signal is set to be a frequency between the subcarrier 173 including the synchronization signal and the subcarrier 174 including the synchronization signal.

[0136] Fig. 16 is a diagram showing an embodiment when the communication system of the present invention is applied to a wireless communication system using a wireless communication system.

As shown in FIG. 16, this embodiment includes a base station 101 and a mobile station 112. Communication is realized by transmitting and receiving radio wave 111 between base station 101 and mobile station 112.

Base station 101 further includes network communication unit 102, radio modulation unit 103, synchronization signal insertion unit 104, synchronization signal generation unit 105, base station radio unit 109, and base station antenna 110. ing.

[0139] In addition, mobile station 112 is synchronized with mobile station antenna 113, mobile station radio section 114, band search step generation section 115, band search step change section 116, and synchronization frequency candidate calculation section 117. The detection unit 118, the radio demodulation unit 119, the decoding unit 120, and the output unit 121 are configured.

[0140] The network communication unit 102 receives a signal received by the network. Radio modulation section 103 performs, for example, IFFT (Inverse Fast Fourier Transform) or IF (Fast Fourier Transform) modulation on the signal received by network communication section 102 by, for example, OFDM communication. Do. The synchronization signal generator 105 is used to synchronize with the mobile station 112. Generates a synchronous signal that can be delayed or repeats the same pattern on the time axis, or a known signal that can be synchronously detected. The synchronization signal insertion unit 104 inserts the synchronization signal generated by the synchronization signal generation unit 105 around the frequency at which the mobile station 112 can detect the synchronization signal in the largest possible band search step. Base station radio section 109 includes a transmitter and an amplifier, and transmits the output signal of synchronization signal insertion section 104 as radio wave 111 from base station antenna 110.

Mobile station radio section 114 includes a receiver and an amplifier, and receives radio wave 111 transmitted from base station antenna 110 via mobile station antenna 113. The band search step generator 115 generates and stores a plurality of band search steps. Band search step changing section 116 selects one band search step from a plurality of band search steps. At this time, a large value is first selected, and then a small value is selected step by step. The synchronization signal frequency candidate calculation unit 117 calculates a synchronization signal candidate frequency using a predetermined calculation formula of the band search step force selected by the band search step change unit 116. The synchronization detection unit 118 detects whether there is a synchronization signal at the candidate frequency by using delay detection or synchronization detection. Radio demodulation section 119 performs FFT or IFFT for OFDM demodulation using the timing at which synchronization is detected by synchronization detection section 118. Decoding section 120 decodes the signal demodulated by radio demodulation section 119. The output unit 121 displays the signal decoded by the decoding unit 120 or outputs sound from a speaker.

Here, when synchronization detection fails in synchronization detection section 118, synchronization signal frequency candidate calculation section 117 designates the next candidate frequency for the same band search step force as before according to a predetermined formula, and synchronization detection section 118 The synchronization detection is performed again.

[0143] When there is no candidate frequency calculated from the same band search step in the search band, the band search step changing unit 116 selects the next band search step, and the synchronization signal frequency candidate calculating unit. In 117, a candidate frequency is designated according to a predetermined formula from a new band search step, and synchronization detection is performed again in synchronization detection unit 118.

[0144] In the configuration shown in FIG. 16, the radio modulation unit 103 and the radio demodulation unit 119 are not limited to OFDM, but may be MC-CDMA (Multi-Carrier Code Division Multiple Access) or FDMA (Fr A communication method such as (equency division multiple access) may be used. In addition to the wireless communication method, a wired communication method may be used.

[0145] FIG. 17 is a diagram showing a form in which another configuration is used for the part shown by a broken line in the form shown in FIG.

As shown in FIG. 17 (a), the present embodiment is different from the portion shown by the broken line in the form shown in FIG. 16 in that the mobile station radio unit 122, the synchronization signal frequency candidate calculation unit 123, The configuration of the synchronization detection unit 126 is different.

[0147] The synchronization signal frequency candidate calculation unit 123 controls the oscillator of the mobile station radio unit 122 composed of superheterodyne and direct convergence, and the synchronization signal candidate frequency is the baseband frequency (= 0Hz) or constant. And control to enter the synchronization detection unit 126.

That is, the n-th stage synchronization signal candidate frequency is fpch—c (n), and the radio frequency specified by down-conversion in the mobile station radio unit 122 at this timing n is fradio (n) Then, fpch_c (n) becomes as shown in Equation 23. However, in this case, the data delay from the mobile station radio unit 122 to the synchronization detection unit 126 is taken into consideration.

[0149] [Equation 23]

[0150] The relationship with the function f (k, Ntmp) shown in Figs. 7 (a) to 7 (d) is as shown in Equation 24, Equation 25, Equation 26, and Equation 27.

[0151] [Equation 24] f _pch _ _c (0) = (0, 0)… (Formula 2 4)

[0152] [Equation 25]

/ • _{pcA c} (l) = /-(0, 1)… (Equation 2 5) [0153] [Equation 26] A _c (2) = (l, 0)… (Equation 2 6) [0154] [Equation 27] f _pch _ _c (3) = (l, 2)… (Equation 2 7)

Therefore, similarly to f (k, Ntmp), a signal centered on fpch—c (n) is input to the synchronization detection unit 126. The synchronization detection unit 126 always performs synchronization detection around the same OHz or intermediate frequency.

[0156] Also, as shown in Fig. 17 (b), the present embodiment is different in the configuration of mobile station radio section 124 from the portion shown in broken lines in the configuration shown in Fig. 16.

[0157] In mobile radio section 124, the radio section frequency specified by frequency down-conversion at timing n is fradio (n), and the digital frequency specified digitally by synchronization detection section 118 is fdig (n). Then, their relationship is as shown in Equation 28. However, in this case, the data delay from the mobile station radio unit 124 to the synchronization detection unit 118 is not considered.

[0158] [Equation 28] fpch—Λ 2 fradio n) f _dig , r ^ · · · (Equation 2 8)

[0159] Since the radio frequency fradio (n) specified for the mobile station radio unit 124 is analog, changing it requires time to stabilize the frequency.

On the other hand, the method of specifying the digital frequency fdig (n) by the synchronization detection unit 118 generally includes a method of multiplying the received signal by a sin, cos signal. When using delay detection, a method of changing the filter through which the received signal passes can be used. In the case of synchronous detection using a replica signal, there is a method of detecting coincidence by shifting the frequency axis and converting the frequency axis to the time axis in replica generation (IFFT, FFT). The synchronization detection at this time detects a match with a known signal. Alternatively, a match with a replica signal calculated from the known signal using IFFT or FFT is detected. Then, a plurality of signal forces shifted on the frequency axis may be generated, and the generated replica signals may be stored and used.

[0161] At this time, in order to use a plurality of pre-computed and stored replicas, the storage capacity is not sufficient. It becomes a title.

[0162] Therefore, assuming that the range that can be handled by changing only the digital frequency is Δ fdig, if the calculated fpch—c (n) force equation 29 is satisfied, only the synchronization detector is controlled to specify the frequency. Determine. If not satisfied, a method can be used in which the mobile station radio unit 124 is controlled, or both the mobile station radio unit 124 and the synchronization detection unit 118 are controlled to specify the frequency.

[0163] [ _Equation 29] f _radio (nl) -f _dig / 2 <f _pch _ _c in) <f _radia (n- \) + f _djg / 2… (Equation ₂₉ )

Claims

The scope of the claims

[1] In a communication system including a transmission device that transmits a synchronization signal for establishing synchronization and a reception device that establishes synchronization by detecting the synchronization signal,

The receiving device sequentially switches from the thinned thinned interval to the non-thinned one for performing the detection of the synchronization signal,

The communication apparatus is configured to transmit the synchronization signal at an interval that is roughly thinned out by the reception apparatus.

[2] In the communication system according to claim 1,

The synchronization is frequency synchronization, and the establishment of synchronization is detection of an effective communication frequency.The reception device sequentially switches a preset frequency change amount from a large value to a small value, and the frequency is set. Calculating a reception-side candidate frequency for detecting the synchronization signal based on a change amount, detecting the synchronization signal using the calculated reception-side candidate frequency;

When a transmission-side candidate frequency that is a frequency candidate for transmitting the synchronization signal is calculated based on the frequency change amount that is as large as possible, and the transmission-side candidate frequency exists in the system frequency band, the transmission frequency A communication system, wherein a side candidate frequency is determined as a synchronization signal frequency for transmitting the synchronization signal.

[3] In the communication system according to claim 1 or claim 2,

The reception device adds an offset to an integral multiple of the reception-side frequency change amount to obtain the reception-side candidate frequency,

The transmission apparatus adds the offset to an integral multiple of the transmission-side frequency change amount to obtain the transmission-side candidate frequency.

[4] In the communication system according to claim 3,

The receiver sets the offset to 0,

The communication apparatus, wherein the transmission device sets the offset to zero.

[5] In the communication system according to any one of claims 1 to 4,

The transmitter transmits a known signal as the synchronization signal;

The receiving device detects a match between the reception-side candidate frequency and the known signal, or a match between the known signal and a replica signal calculated using IFFT or FFT, and stores the calculated replica signal A communication system.

[6] In the communication system according to any one of claims 1 to 4,

The transmission apparatus transmits a signal that repeats the same pattern as the synchronization signal, and the reception apparatus detects the synchronization signal by delay detection.

[7] In the communication system according to any one of claims 1 to 6,

The transmission device sets the transmission side frequency change amount to an integral multiple of a minimum arrangement unit of a center frequency of the system band.

[8] In the communication system according to any one of claims 1 to 7,

The receiving apparatus sets the amount of frequency change on the receiving side to an integral multiple of a minimum arrangement unit of a center frequency of the system band.

[9] A transmission device that transmits a synchronization signal for synchronization within a system frequency band to a reception device,

[10] In the transmission device according to claim 9,

A transmission apparatus characterized by adding an offset to an integral multiple of the transmission side frequency change amount to obtain the transmission side candidate frequency.

[11] In the transmission device according to claim 10,

A transmission apparatus characterized in that the offset is 0.

[12] A receiver that receives a synchronization signal transmitted from a transmitter, The reception side frequency change amount set in advance is sequentially switched from a large value to a small value, and the reception side candidate frequency for detecting the synchronization signal is calculated based on the reception side frequency change amount. A receiving apparatus that detects the synchronization signal using the calculated reception-side candidate frequency.

[13] The receiving device according to claim 12,

A receiving apparatus, wherein an offset is added to an integer multiple of the receiving side frequency change amount to obtain the receiving side candidate frequency.

[14] The receiving device according to claim 13,

A receiving apparatus, wherein the offset is 0.

[15] Synchronization detection in a communication system having a transmission device that transmits a synchronization signal for synchronization within the system frequency band and a reception device that detects the synchronization signal within the system frequency band A method,

A process of sequentially switching the reception device from performing the synchronization signal detection trial to a non-thinned one roughly

A synchronization detection method comprising: a process of setting transmission so that the transmission device is detected at an interval obtained by roughly thinning out the synchronization signal of the reception device.

[16] In the synchronization detection method according to claim 15,

A process in which the receiving device sequentially switches a preset frequency change amount from a large value to a small value;

When the transmission side candidate frequency is present in the system frequency band, the transmission device uses the transmission side candidate frequency as a synchronization signal frequency for transmitting the synchronization signal. Process to determine as

A synchronization detection method comprising: a process in which the transmission device transmits the synchronization signal to the reception device using the synchronization signal frequency.